1. Field of Invention
The present invention relates to mobile vehicles and, more particularly, is directed to articulated material handling vehicles used in underground mining operations.
2. Description of the Invention Background
In mining operations, especially in the underground mining of coal and the like, a variety of conveying apparatuses are used to transport the mined material from the mining machine to a final destination wherein they can be transported from the mine. During the early stages of mine development, main haulageways are created within the mine and often support stationary belt conveyors for transporting the mined material from the mine or a remote collection area. A variety of different conveying systems and apparatuses have been developed for transferring the mined material from the mining machine to the main belt conveyors or staging areas.
One type of apparatus that is used to transport mined material within a mine between a mining machine or staging area and a conveyor network which ultimately transfers the material out of the mine is known as a shuttle car. In the past, conventional shuttle cars typically comprised wheeled vehicles that were equipped with material-receiving containers. The car was usually electrically powered through cables attached to a remote power source and steered by an operator that rode on the vehicle.
The utility of those early cars was often limited due to their inability to negotiate "tight" corners between the intersecting passages cut within the mine. Thus, the overall size (i.e., width and length) of the car was confined to dimensions that would permit the car to travel between intersecting passages. Therefore, the payload capacity of such a shuttle car was limited.
In more recent years, articulated cars have been developed in an effort to increase the hauling capacity of the car while improving its maneuverability. Early articulated shuttle cars typically included a front tractor portion that housed batteries and supported the operator and a rear container portion that was attached to the tractor portion by an articulated joint arrangement. Examples of such cars are disclosed in U.S. Pat. No. 3,826,387 to Galis, U.S. Pat. No. 3,827,721 to Coval, U.S. Pat. No. 4,011,957 to Bendtsen, U.S. Pat. No. 4,212,365 to Curry, U.S. Pat. No. 4,245,714 to Kersey and U.S. Pat. No. 4,890,684 to Simmons.
To enhance the vehicle's maneuverability within a mine where uneven floor conditions are typically present, it is desirable for the vehicle portions to freely rotate relative to each other about the vehicle's longitudinal axis. Also, to enable the vehicle to traverse undulations in the mine floor, it is desirable for the vehicle portions to be capable of pivoting about an axis that is transverse to the longitudinal axis. Furthermore, to enable the vehicle to negotiate relatively sharp corners within a confined space such as an underground mine, it is desirable for the vehicle portions to be capable of being selectively pivotable relative to each other about a vertical axis.
Some prior vehicles have some of the above-mentioned capabilities. However, due to their particular joint construction, such variable articulation is somewhat limited. For example, U.S. Pat. No. 3,826,387 to Galis discloses an articulated haulage vehicle that has a hopper portion that is pivotally attached to a prime mover portion such that the two portions are capable of selective pivotal motion about a vertical axis by a pair of hydraulic cylinders. The vehicle is not equipped to "roll" about a longitudinal axis or pivot about a horizontal axis.
U.S. Pat. No. 3,827,721 to Coval discloses an articulated haulage vehicle that has a front portion and a rear portion that are connected together by spherical bearing arrangements that permit the vehicle sections to pivot about a plurality of axes in response to undulations in the mine floor. Such spherical bearing arrangements, however, are typically not well-suited for the rigors of underground mining and often fail prematurely and/or require frequent maintenance or repair.
Another articulated material handling vehicle is disclosed in U.S. Pat. No. 4,011,957 to Bendtsen and includes a rear trailer unit that is pivotally attached to a front tractor unit by a hitch assembly. The hitch assembly includes a vertically arranged pivotal coupling that permits the trailer and tractor portions to be pivoted about a vertical axis by a pair of jacks. The hitch assembly also includes a horizontally arranged pivotal coupling that enables the tractor and trailer to pivot about a longitudinal axis of oscillation. This joint arrangement, however, does not permit the tractor and trailer to pivot relative to each other about a transverse horizontal axis.
U.S. Pat. No. 4,212,365 to Curry discloses a pivot connection and a tilt mechanism for interconnecting portions of an articulated vehicle together. The pivot connection is provided between the vehicle portions to enable them to turn relative to each other. The tilt mechanism includes a horizontal pivot connection between the two vehicle portions so that vertical movement of at least a portion of one vehicle adjacent to the horizontal pivot connection will move a portion of the other vehicle adjacent to the pivot connection in the same direction and cause the other vehicle to pivot about the axis of its wheels. This joint arrangement, however, does not permit the vehicle sections to pivot about a longitudinal axis.
U.S. Pat. No. 4,245,714 to Kersey discloses an articulated mining vehicle that includes front and rear vehicle portions connected by a "floating" connector member. The connector member has upper and lower vertically aligned pivot connections attached to the rear vehicle portion and horizontally aligned front and rear pivot connections attached to the front vehicle portion. This joint arrangement utilizes a plurality of spherical bearings which tend to fail under normal service loads.
U.S. Pat. No. 4,890,684 to Simmons discloses an articulated vehicle with a hinged joint that enables the portions of the vehicle to pivot relative to each other about three axes extending at right angles to each other. A hydraulically operated strut extends between the two vehicle sections and is universally pivoted at its ends to the two vehicle sections to control the relative pivoting of the two vehicle sections about a transverse axis while enabling the middle of the vehicle to be raised or lowered for various reasons. The vehicle is steered by a pair of hydraulically operated steering struts. The hydraulically actuated struts are connected to the vehicle sections by spherical bearing arrangements that are susceptible to failing under normal operating loads.
Other joint arrangements for articulated vehicles are disclosed in U.S. Pat. No. 1,610,902 to Tomlinson, U.S. Pat. No. 3,773,129 to Anderson, U.S. Pat. No. 2,179,955 to Rawnsley and U.S. Pat. No. 3,035,654 to Nuttall, Jr. et al. However, none of those patents disclose a joint arrangement that enables the vehicle sections to pivot relative to each other about a longitudinal axis, a vertical axis and a transverse horizontal axis and that is reliable and easy to maintain.
Accordingly, there is a need for a joint arrangement for an articulated vehicle that enables the vehicle portions to pivot relative to each other about a longitudinal axis, a vertical axis and a transverse horizontal axis that is capable of withstanding the abuse commonly encountered during underground mining operations and that is easy to access for maintenance purposes.